1. Field of the Invention
The present invention relates to a tone generator and an electronic instrument for generating a single tone signal by mixing tone component signals obtained by tone generating units, and a storage medium for computer readably storing processing steps for implementing that.
2. Description of the Related Art
Conventionally, for example, an electronic instrument generates a single tone signal corresponding to a key touch from tone component signals such as soft, middle, and loud tone components. For this purpose, a tone generator with the arrangement as shown in FIG. 1 is prevalently used in an electronic instrument.
More specifically, as shown in the above FIG. 1, an electronic instrument has three tone generating units 901 to 903. The first, second, and third tone generating units 901, 902, and 903 respectively read out waveform data 911, 912, and 913, which are stored in a waveform memory (not shown) and respectively serve as soft, middle, and loud tone components, and generate and output soft, middle, and loud tone component signals 921, 922, and 923. That is, the first tone generating unit 901 generates the soft tone component signal 921 corresponding to a soft key touch from the waveform data 911, the second tone generating unit 902 generates the middle tone component signal 922 corresponding to a middle key touch form the waveform data 912, and the third tone generating unit 903 generates the loud tone component signal 923 corresponding to a hard key touch from the waveform data 913. One tone signal for a key touch performing by the player is generated with changing the mixing ratio of the aforementioned soft, middle, and loud tone component signals 921, 922, and 923 in accordance with the intensity of the key touch.
For example, in case of a soft key touch, a tone signal for the key touch is generated and output using only the soft tone component signal 921 generated by the first tone generating unit 901.
On the other hand, in case of a middle key touch, the second tone generating unit 902 generates the middle tone component signal 922, and a tone signal corresponding to the key touch is generated and output by mixing this middle tone component signal 922 and the soft tone component signal 921 generated by the first tone generating unit 901. At this time, as the key touch becomes harder, the mixing ratio of the middle tone component signal 922 of the second tone generating unit 902 increases, and inversely the mixing ratio of the soft tone component signal 921 of the first tone generating unit 901 decreases. Finally, the mixing ratio of the soft tone component signal 921 becomes "0" to leave the middle tone component signal 922 alone. In this manner, a tone ranging from a soft key touch to a middle key touch can smoothly change.
In case of a hard key touch, the third tone generating unit 903 generates the loud tone component signal 923, and a tone signal for the key touch is generated and output by mixing this loud tone component signal 923 and the middle tone component signal 922 generated by the second tone generating unit 902. Also at this time, as the key touch becomes harder, the mixing ratio of the loud tone component signal 923 of the third tone generating unit 903 increases, and inversely the mixing ratio of the middle tone component signal 923 of the second tone generating unit 902 decreases, thereby smoothly changing the tone ranging from a middle key touch to a hard key touch. But, since the loud tone component signal 923 does not contain any soft tone component signal (a signal in the low frequency range), the mixing ratio of the middle tone component signal 922 must not be set at "0". That is, the middle tone component signal 922 must always be output.
However, as described above, in the conventional arrangement for generating a tone signal, individual tone component signals are generated and mixed from units of waveform data as sources for a single tone signal, while changing the mixing ratio at that time in accordance with the key touch intensity, thereby generating a tone signal for the key touch. According to this arrangement, a change in tone color can be implemented in accordance with the player's key touch, but the waveform data of all tone components (soft, middle, and loud tone components, and the like) must be stored in a waveform memory.
Besides, when generating and producing a single tone signal, tone generation channels of a sound source LSI corresponding to the types of tone component signals used for that are required. For example, when one tone signal is generated and produced from three tone component signals, i.e., soft, middle, and loud tone component signals, three tone generation channels are used. For this reason, even when the total number of tone generation channels of the sound source LSI is 48, the number of tones that are actually produced at the same time is 16 (48.div.3=16). That is, when a single tone signal is produced, the number of tones that are produced at the same time decreases with increasing the number of tone component signals used for that.
For example, Japanese Patent Laid-Open Nos. 1-257898, 1-269995, and the like, describe an arrangement for generating a single tone signal by obtaining kinds of waveform data by filtering a single unit of waveform data, and synthesizing (mixing) those waveform data. With this arrangement, however, though the waveform memory size can be saved since only the single unit of waveform data as a source for generating a tone signal need only be stored in the waveform memory, the tone generation channels corresponding to the kinds of waveform data (which are actually used to generate a tone signal) obtained by filtering that waveform data are required, and the number of tones that are produced at the same time decreases accordingly.
Therefore, since tone generation channels of the sound source LSI must be used in accordance with the number of tone component signals used to generate a tone signal, conventionally the limited tone generation channels of the sound source LSI cannot effectively be used. Also, when the number of kinds of tone component signals is increased to implement a larger change in tone color, the number of tones that are produced at the same time decreases accordingly, and hence, the number of tone generation channels of the sound source LSI must be increased, thus increasing circuit scale.